EternalSynergy-Based Exploit Targets Recent Windows Versions

A security researcher has devised an EternalSynergy-based exploit that can compromise versions of Windows newer than Windows 8.

EternalSynergy is one of several exploits allegedly stolen by the hacker group calling themselves the Shadow Brokers from the National Security Agency (NSA)-linked Equation Group. The exploit was made public in April along with several other hacking tools, one month after Microsoft released patches for them.

In May, a security researcher included EternalSynergy and six other NSA-linked hacking tools (EternalBlue, EternalChampion, EternalRomance, DoublePulsar, Architouch, and Smbtouch) in a network worm called EternalRocks. The tool was pulled weeks later to prevent abuse.

Security researcher Worawit Wang has now made public an EternalSynergy-derived exploit that also leverages EternalRomance and can be used on a wider range of Windows versions.

Available on both GitHub and ExploitDB, the tool targets 64-bit versions of Windows 2016, Windows 2012 R2, Windows 8.1, Windows 2008 R2 SP1, and Windows 7 SP1, as well as the 32-bit versions of Windows 8.1 and Windows 7 SP1.

Security researcher Sheila A. Berta, who is part of Telefonica's Eleven Paths security unit, has published a paper (PDF) on how to exploit Wang’s tool to get a Meterpreter session on Windows Server 2016.

EternalSynergy is based on the CVE-2017-0143vulnerability, which “stems from not taking the command type of an SMB message into account when determining if the message is part of a transaction,” Microsoft reveals. “In other words, as long as the SMB header UID, PID, TID and OtherInfo fields match the corresponding transaction fields, the message would be considered to be part of that transaction.”

According to Microsoft, EternalSynergy should not work on Windows iterations newer than Windows 8, due to kernel security improvements such as Hypervisor-enforced Code Integrity (HVCI), which prevents unsigned kernel pages from being executed, and Control Flow Guard (CFG), designed to prevent invalid indirect function calls.

The exploit is expected to crash on unsupported operating system releases, but Wang managed to create a stable tool that targets Windows XP and newer versions, except Windows 10. Given a patch is already available from Microsoft, impacted users should consider applying it as soon as possible.